request.Match check Response bit as well (#1775)

* request.Match check Response bit as well

We should check this bit and reject them as invalid.

* Fix test

request/request.go

@@ -380,6 +380,10 @@ func (r *Request) Match(reply *dns.Msg) bool {
 		return false
 	}
 
+	if reply.Response == false {
+		return false
+	}
+
 	if strings.ToLower(reply.Question[0].Name) != r.Name() {
 		return false
 	}

request/request_test.go

@@ -162,6 +162,7 @@ func TestRequestScrubAnswerExact(t *testing.T) {
 func TestRequestMatch(t *testing.T) {
 	st := testRequest()
 	reply := new(dns.Msg)
+	reply.Response = true
 
 	reply.SetQuestion("example.com.", dns.TypeMX)
 	if b := st.Match(reply); b {